1. Field of the Invention
This invention relates to a fuel cell system having a compressor and a regenerator.
2. Description of the Related Art
A compressor and regenerator for a fuel cell is connected to a fuel cell in a fuel cell device used for a car as, for example, described in Japanese Unexamined Patent Publication (Kokai) No. 7-14599. In fuel cells in general, a pair of separators is disposed one on each side of an electrolyte layer. Feed grooves for supplying fuel and an oxygen-containing gas are formed in these separators. One of the separators supplies a hydrogen-containing fuel and the other separator supplies an oxygen-containing gas such as air. In consequence, electrons move, due to the chemical reaction between hydrogen and oxygen, to provide a current. A fuel feed pipe and an air feed pipe are connected to the upstream side of such a fuel cell to supply the fuel and air, respectively. The air feed pipe is open to the atmosphere through a compression mechanism portion that is driven by a motor. The compression mechanism portion pressurizes air from the atmosphere to a predetermined pressure and supplies the air to the fuel cell. An air exhaust pipe is connected to the downstream side of the fuel cell to exhaust an exhaust gas, after oxygen is extracted from air inside the fuel cell, to the atmosphere. A regenerative mechanism portion is connected to the air exhaust pipe so as to assist the motor operating the compression mechanism portion, using power that is generated as the exhaust gas is expanded. In the fuel cell device of this kind, each of the compression mechanism portion and the regenerative mechanism portion use a separate compressor and regenerator for a fuel cell. In this fuel cell device, the compression mechanism portion and the regenerative mechanism portion are constituted so that they can be operated by the same driving source.
However, the conventional compressor and regenerator. for a fuel cell involves the problem that it takes large installation area and its mountability in a car, for example, is bad, because the compression mechanism portion and the regenerative mechanism portion are separate from each other. This problem may be solved if the compression mechanism portion and the regenerative mechanism portion are integrated with each other.
Even if the compression mechanism portion and the regenerative mechanism portion are thus integrated, another problem remains to be solved. If a compression chamber and a regenerative chamber are. greatly spaced apart from each other, the route of a pipe for connecting the compression chamber and the regenerative chamber through the fuel cell is long, and a pressure loss in the oxygen-containing gas is likely to occur in the interim. Therefore, the oxygen-containing gas does not have sufficient pressure when supplied to the fuel cell, with the result that power generation performance of the fuel cell drops, or the regenerative mechanism portion cannot sufficiently assist the driving source because an exhaust gas having sufficient pressure is not supplied thereto.
To cope with this problem, the compression chamber for increasing the pressure of the oxygen-containing gas to a high pressure in the compression mechanism portion and the regenerative chamber for assisting the driving source by the exhaust gas in the regenerative mechanism portion may be disposed adjacent to each other. In this case, however, the exhaust gas is likely to form a by-path leaked from the regenerative chamber side to the compression chamber side. In other words, oxygen of the exhaust gas is to be extracted in the fuel cell. Therefore, if exhaust gas having a low density of oxygen leaks to the compression chamber, the pressure of this exhaust gas having a low density of oxygen is elevated to a high pressure in the compression mechanism portion and is then supplied to the fuel cell. In this case, a sufficient amount of oxygen for generating a current in the fuel cell cannot be supplied, and power generation performance of the fuel cell consequently drops.
In view of the problems described above, it is an object of the present invention to provide a compressor and regenerator for a fuel cell that can sufficiently assist a driving source and can ensure a high power generation performance of a fuel cell.
A compressor and regenerator for a fuel cell according to the present invention includes a compression mechanism portion having a compression chamber for pressurizing an oxygen-containing gas to a high pressure to supply this oxygen-containing gas to a fuel cell; and a regenerative mechanism portion having a regenerative chamber for assisting a driving source by an exhaust gas exhausted from the fuel cell; wherein the compression mechanism portion and the regenerative mechanism portion are constituted in such a manner as to be operated by the same driving source; wherein the compression chamber and the regenerative chamber are disposed adjacent to each other; and wherein sealing means, for preventing a leaked by-path of the exhaust gas from the regenerative chamber to the compression chamber, is interposed between the compression chamber and the regenerative chamber.
In the compressor and regenerator for a fuel cell according to the present invention, the compression mechanism portion and the regenerative mechanism portion are so constituted as to be operated by the same driving source and are integrated with each other. Therefore, the installation area is small, and excellent mountability to a car, for example, can be achieved.
In the compressor and regenerator for a fuel cell according to the present invention, the compression chamber and the regenerative chamber are disposed adjacent to each other. Therefore, the route for pipes for connecting the compression chamber to the regenerative chamber through the fuel cell becomes short, and the pressure loss in the oxygen-containing gas does not occur so easily in this route. Therefore, the oxygen-containing gas retains a pressure sufficient for it to be supplied to the fuel cell, and a good power generation performance of the fuel cell can be maintained. An exhaust gas having a sufficient pressure is supplied to the regenerative mechanism portion, and the power of the driving source can be sufficiently assisted.
In the compressor and regenerator for a fuel cell according to the present invention, sealing means for preventing a leaked by-path of the exhaust gas to the compression chamber is interposed between the compression chamber and the regenerative chamber. Therefore, the sealing means prevents the exhaust gas, that has a low density of oxygen, from forming a by-path leaked to the compression chamber and can thus prevent the exhaust gas having a low density of oxygen from being pressurized by the compression mechanism portion and supplied to the fuel cell. In consequence, oxygen can be supplied in a sufficient amount for generating the current in the fuel cell, and power generation performance of the fuel cell can be maintained.
For these reasons, the compressor and regenerator for a fuel cell according to the present invention can sufficiently assist the driving source and can keep the power generation performance of the fuel cell high.
The compression mechanism portion constituted as a scroll type includes a housing, one surface of a side plate which orbit by the rotation of a drive shaft and a first spiral member protruding from this surface. The regenerative mechanism portion constituted as a scroll type includes the housing forming the compression mechanism portion, the other surface of the side plate opposite to the surface of the side plate forming the compression mechanism portion, and a second spiral member formed on this other surface to protrude therefrom. This construction can provide a quiet and light compressor and regenerator for a fuel cell. Because the compression mechanism portion and the regenerative mechanism portion can share the side plate from which the first and second spiral members protrude, the total length in the axial direction inclusive of the driving source can be reduced. Therefore, the compressor and regenerator has excellent mountability to a car, for example. In this compressor and regenerator for a fuel cell, the sealing means is formed between the housing, that constitutes the compression mechanism portion and the regenerative mechanism portion, and the side plate that constitutes the compression mechanism portion and the regenerative mechanism portion.
Such a sealing means comprises a ring-like zone formed by the housing and the side plate, in which at least one of the surfaces of the side plate and the housing always oppose each other, a seal ring groove formed annularly in the ring-like zone, and a seal ring fitted in the seal ring groove and coming into sliding contact with the side plate or the housing. This structure can enable the exhaust gas in the ring-like zone to apply a suitable back pressure to the seal ring in the seal ring groove. Due to the movement of the side plate, the seal ring in the seal ring groove is urged towards the side plate or the housing on the basis of the Bernoulli""s theorem. In this way, the exhaust gas in the regenerative chamber is sealed by the seal ring and is prevented from being by-passed to the compression chamber.
If the exhaust gas is sealed by only applying the back pressure, a little amount of the exhaust gas may be by-passed, depending upon a degree of the back pressure. Therefore, the seal ring is preferably urged towards the side plate or the housing by an urging means. If so, the seal ring is urged towards the side plate or the housing by the urging means despite the degree of the back pressure, and the exhaust gas securely prevents from by-passing.
An O-ring, that is commercially available and relatively economical, can be used for the urging means. This O-ring is preferably stored in the seal ring groove squeezed to some extent without creating clearance in the width direction of the seal ring groove. If any clearance is created in the width direction of the seal ring groove, the seal ring is deviated from the O-ring in the seal ring groove. In such a case, the O-ring is likely to fail to urge the seal ring towards the side plate or the housing.
O-rings have various shapes such as an ordinary solid circular section type, an X-shaped section type, an H-shaped section type, a C-shaped section type, a hollow type, and so forth. Among them, the O-ring having an ordinary solid circular section type is likely to invite a large change of reaction with respect to a squeeze and to eventually invite a great variance of quality of the compressor and regenerator for a fuel cell. Therefore, an O-ring having the X-shaped section, an O-ring having the H-shaped section, an O-ring having the C-shaped section or an O-ring having the hollow shape is preferably used. Particularly when the O-ring having an X-shaped section is employed, the exhaust gas can enter the clearance of this O-ring, and the seal ring can be urged more easily towards the side plate or the housing by the urging force of the O-ring and the pressure of the exhaust gas. As a result, the prevention effect of by-passing of the exhaust gas becomes greater.
The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.